Routing Slip in Word/Outlook XP

Sorry if this has been asked before, but I couldn’t find it though the search facility.

When I choose File/Send to/Routing recipient in Word, the program goes through the proper sequence and I am able to choose a name from the Contacts I have in Outlook. However, Outlook then tell me that it doesn’t recognise “Unknown” as the sender. I can send and receive from Outlook as normal at other times.

As far as I know Outlook and Word are installed and configured correctly.

Has anybody any ideas as to what is causing this, please? Am I missing something obvious? If so, apologies!

Many thanks in advance.

David